docs: def com_google_fonts_check_smart_dropout(ttFont):
    """Font enables smart dropout control in "prep" table instructions?
  
    B8 01 FF    PUSHW 0x01FF
    85          SCANCTRL (unconditinally turn on
                          dropout control mode)
    B0 04       PUSHB 0x04
    8D          SCANTYPE (enable smart dropout control)
  
    Smart dropout control means activating rules 1, 2 and 5:
    Rule 1: If a pixel's center falls within the glyph outline,
            that pixel is turned on.
    Rule 2: If a contour falls exactly on a pixel's center,
            that pixel is turned on.
    Rule 5: If a scan line between two adjacent pixel centers
            (either vertical or horizontal) is intersected
            by both an on-Transition contour and an off-Transition
            contour and neither of the pixels was already turned on
            by rules 1 and 2, turn on the pixel which is closer to
            the midpoint between the on-Transition contour and
            off-Transition contour. This is "Smart" dropout control.
    """
    INSTRUCTIONS = b"\xb8\x01\xff\x85\xb0\x04\x8d"
  
    if ("prep" in ttFont and
        INSTRUCTIONS in ttFont["prep"].program.getBytecode()):
      yield PASS, ("'prep' table contains instructions"
                    " enabling smart dropout control.")
    else:
      yield FAIL, ("'prep' table does not contain TrueType "
                    " instructions enabling smart dropout control."
                    " To fix, export the font with autohinting enabled,"
                    " or run ttfautohint on the font, or run the "
                    " `gftools fix-nonhinting` script.")